The constant change *is what killed* Sublevel. Nobody could rely on features being available as they kept being pulled or changed so frequently -- messages, API, images. Even when I was away, there's posts about the "chat UI" being gone? If you want to retain users, perhaps do these experiments on a subdomain, and ask for people's feedback? Involve the community because *we care* about this product; changes affect us.
I think the shuffling of domains was more jarring than feature changes. I think I got a glimpse of the reasoning behind it, and briefly used both sites, but it did slow me down from re-engaging until things seemed more stable.